Hybridisierung und Regelung eines mobilen Direktmethanol-Brennstoffzellen-Systems

Wilhelm, Jörg Wilhelm

Dissertation / PhD Thesis/Book

Hybridisierung und Regelung eines mobilen Direktmethanol-Brennstoffzellen-Systems

Wilhelm, J. W. (Corresponding author)FZJ*

2010
Forschungszentzum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-89336-642-2

Jülich : Forschungszentzum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich : Energie & Umwelt / Energy & Environment 73, 220 S. (2010) = RWTH Aachen, Diss., 2010

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Please use a persistent id in citations: http://hdl.handle.net/2128/3788

Abstract: Direct methanol fuel cells (DMFCs) are characterized by the fact that they directly convert the chemical energy of the liquid fuel methanol into electrical energy. Methanol has a high energy density and can be stored relatively easily. Due to these advantages, direct methanol fuel cell systems are suitable, for example, as a battery replacement for light-traction applications in the kW class. Since refuelling is much faster than recharging a battery, almost interruption-free operation is possible. The aim of this thesis is therefore to develop a direct methanol fuel cell system for lighttraction applications. The systems technology development and characterization of a mobile direct methanol fuel cell system is initially examined in general and then applied to the example of a horizontal order picker, a type of forklift truck. A hybridization and control concept is developed for this type of truck. The procedure is structured into the theoretical characterization of the application, the development of theoretical concepts and a concluding systems analysis using data from the test stand and simulations. The characteristic driving cycle of the application results from the characterization. The concept development is based on key data such as maximum peak power during acceleration and braking as well as average power. The two-stage theoretical development of a hybridization concept is based on a pure fuel cell vehicle. A systems analysis of all possible concepts with respect to the criteria of fuel cell power, total system efficiency and dynamic fuel cell loading eventually leads to the preferred concept of indirect coupling. A cascade controller with map control, the control concept developed for this purpose, keeps the energy storage unit at a constant state of charge and provides for the fuel cell aging protection as well as aging detection. The driving cycle, operational states of the vehicle and the efficiencies of the individual components play a decisive role for the dimensioning of the fuel cell as well as of the energy storage unit. Variation of parameters results in a minimum required fuel cell power of 1.3 kW as well as a minimum energy density of 66 Wh/l or a minimum power density of 355 W/l for the energy storage unit, respectively. The high energy density required and the fact that the energy storage unit must always be operated at a partial state of charge leads to faster aging, particularly of lead-acid batteries, so that a lithium battery is eventually chosen as an energy storage unit.

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